GB2197701A - Clutch type disc brake - Google Patents

Abstract

A clutch type disc brake is provided with a housing, at least two axially displaceable brake discs (14) arranged in the housing at least four friction surfaces (12, 15) out of which in each case two are arranged on both sides of one brake disc (14), and an actuating device having at least two actuating cylinders (6) with actuating pistons (7a, b) arranged therein, which actuating device is arranged between two friction surfaces. The actuating cylinders (6) are at least partially arranged in two central pieces (1, 2) of the housing, the central pieces (1, 2) of the housing forming a hollow space (5) communicating with a coolant inlet and a coolant outlet (A, B). A valve (not shown) in the pressure oil inlet to the actuating device controls return of the pistons (7a, 7b) on brake release, so as to compensate for brake wear. <IMAGE>

Description

CLUTCH TYPE DISK BRAKE This invention relates to a clutch type disc brake of the kind having a housing, at least two axially displaceable brake discs arranged in the housing, at least four friction rings out of which in each case two are arranged on both sides of one brake disc, and an actuating device having at least two actuating cylinders with actuating pistons arranged therein, which actuating device in each case is arranged between two friction rings.

Such disc brakes are primarily used in heavy tracklaying vehicles. The thermal stress on the brake is very high because of the great bulk to be braked in such heavy vehicles. In particular, there exists the danger of the pressure medium's temperature rising too much.

In known clutch type disc brakes, in most cases, there is no cooling provided for the brake or, otherwise, cooling is achieved by very intricate and expensive measures.

It is thus an object of this invention to provide a clutch type disc brake of the kind referred to which reliably solves the thermal problems in an easy and costsaving manner.

According to the invention there is provided a clutch type disc brake of the kind having a housing, at least two axially displaceable brake discs arranged in the housing, at least four friction rings out of which in each case two are arranged on both sides of one brake disc, and an actuating device having at least two actuating cylinders with actuating pistons arranged therein, hich actuating device in each case is arranged between two friction rings, characterised in that the actuating cylinders are at least partially arranged in two central pieces of the housing, these central pieces of the housing forming a hollow space provided with a coolant inlet and with a coolant outlet.

Thanks to this solution it is achieved that the heat can be carried off by the coolant as near as possible to its origin. Two completely identical parts are preferably used as central pieces of the housing.

An optimum effective friction diameter is obtained by the fact that at least two pad resetting devices are arranged in the area between two friction rings and need not extend on the outside over the brake discs as known clearance springs have to.

By using outside cooling plates, heat forming at the outside pad rings is also safely carried away.

An overall low temperature is achieved by arranging the linking bridges in the hollow space penetrated by the coolant. The fact that the linking bridges used as repetition parts have no parallel flange surfaces, but rather form a predetermined angle in respect of each other, enables an advantageous tolerance compensation between the connecting surfaces of the actuating cylinders.

The clearance valve allows an automatic hydraulic clearance limitation to be achieved in an advantageous manner, a susceptible mechanical adjusting device thus becoming superfluous.

The predetermined clearance can be maintained in an optimal way by the fact that a connection connectible with at least one pressue consumer communicates with the pressure generator indirectly, on the one hand, via a movable wall such as a piston or a diaphragm and, on the other hand, directly with the pressure generator connection via a prestressed seat valve. In such an arrangement it is particularly suitable for the volume displaceable by the movable wall to equal the volume which has to be carried away from the pressure consumer for ventilating the brake.

If large volumes have to be displaced upon an application of the brake it will be particularly favourable if another seat valve is provided which is actuatable by the movable wall.

Little expenditure in terms of components is required in an embodiment where the two seat valves are prestressed by one common spring.

In an embodiment where the piston serving as a movable wall is designed as a differential piston whose larger pressurisation surface is pressurisable by the pressure of the pressure generator it is ensured that the piston is always displaced into an end position first before, if necessary, the seat valve opens and further pressure medium can flow to the pressure consumer.

Particularly favourable is a combination of the clearance valve with a pad resetting device.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is an axial section through a clutch type disc brake; Figure 2 is a section along M-M and N-N as per Figure 1; Figure 3 shows a clearance valve according to an embodiment of this invention; and Figure 4 shows another embodiment of a clearance valve.

The embodiment of this invention which is illustrated in Figures 1 and 2 shows a preferably watercooled clutch type disc brake, in particular for a tracklaying vehicle. This brake has two identical annular central pieces 1,2 of the housing which partially surround the hub 32 fastened on the shaft 30.

Connections for the coolant outlet B and for the coolant inlet A are provided at the central pieces of the housing 1,2. The two central pieces of the housing are screwed together by means of screws 4, with a seal 3 inserted in between, and form an annular symmetrical hollow space 5 communicating with the coolant inlet A and with the coolant outlet B. Respectively six actuating cylinders 6 as well as bowl-type spring retainers 8 are distributed evenly and in alternating succession over the circumference of the hollow space 5. Before assembling the two central pieces 1,2 of the housing, the bowl-type spring retainers 8 have been passed through corresponding recesses in the front faces of the central pieces 1,2 of the housing and are fixed axially by stop collars 34 and 35 between the two central pieces of the housing.The front faces of the actuating cylinders 6 and of the bowltype spring retainers 8 are flush with the respective front faces of the central pieces of the housing.

Over 1800, in each case, the actuating cylinders 6 of one brake half are connected with -each other and communicate with the pressure connections C, E and the ventilation connections D, F. The connection from one actuating cylinder 6 to the other is affected by linking bridges 10.

The communication towards the pressure oil connections and towards the ventilation connections is affected by connecting bridges 9. The flange surfaces G, H of the linking bridges 10 are not parallel, to each other, but together form an angle (in this case: 600), whereby it is possible to compensate tolerances between the connecting surfaces of the actuating cylinders 6. .As all the actuating cylinders 6 have to be hydraulically connected in their plane of symmetry normal in respect of their cylindrical axis, the pressure oil channels in the connecting bridges 9 do not extend in the central plane - as is the case with the linking bridges 10, which are identical among themselves, but rather lead outwardly of the latter at an angle and into one of the central pieces 1 and 2 of the housing whence they are passed radially outwards. The pressure oil passages are each sealed so as to prevent coolant from leaking out.

In the actuating cylinders 6 two actuating pistons 7a,7b are arranged in each case in an axially movable and sealed manner. The actuating pistons 7a,7b designed as hollow pistons face each other with their arched front sides, while the annular surface of the open end in each case acts on a contact ring Ila, llb. In each case on the contact ring's ila and lib side averted from the actuating piston 7a and 7b, the inside pad segements 12 are fastened by means of a plurality of clamping sleeves 13. The two brake discs 14 guided axially displaceable on the hub 32 by means of a serration can be acted upon by the inside pad segments 12. The brake disc 14 is fastened on the brake disc base 33 by means of several clamping sleeves 31, the brake disc base 33 being supported in the serration on the hub 32. The brake discs 1A acted upon by the pistons 7a, 7b, the contact rings llz, lib, and the inside pad segments 12 are axially supported in the outward direction on the outside pad segments 15 fastened at the outside cooling plates 16 by means of clamping sleeves 13. Tension rod screws 21 clamp the outside cooling plates 16 and the brake housing rings 17 to the central pieces 1,2 of the housing. With this design it is ensured that all the coolant seals 3,22,23 are only stressed by the required sealing forces, yet not by shearing forces.

The outside cooling plates 16 have coolant inlets 20 and (non-illustrated) coolant outlets through which the coolant can enter the cooling chambers 29. So as to secure the contact rings 11a and 11b against twisting, recesses 18 are provided in the brake housing rings 17.

The axially displaceable engaging tongues 19 of the contact discs are supported in the recesses 18.

Compression springs 24 are provided in the bowl-type spring retainers 8 and, in altenating succession, act on the contact rings 112 and 1lb via tie bolts 25. To this end, the semi-spherical, enlarged end of the tie bolt 25 is supported in a corresponding recess of the contact ring 11 while the bolt itself protrudes into the bowltype spring retainer with its other end provided with a disc-shaped radial enlargement. The middle part of the bolt is surrounded by a compression spring ?4 which is supported on a front side of the bowl-type spring retainer 8, on the one hand, and on the radial discshaped enlargement of the tie bolt 25, on the other hand.

In this manner, the contact rings 11a and 11b are drawn towards each other and ensure ventilation of the brake.

Thanks to the described design of the brake, nearly all operating parts and housing parts are constructed as repetition parts. The twin brake is suitable both for right hand and left hand versions. If necessary, it is possible to combine a quadruple brake out of the twin brake where again each of the - in that case - four brake discs can be cooled actively from both sides So as to prevent the two actuating pistons 7a and 7b which move in opposite directions from returning into the initial position after any braking operation in the case of progressive pad wear, a hydraulic clearance valve is connected between the braking pressure generator and the pressure oil connections C and E.

The clearance valve illustrated in Figure 3 has a housing composed of the housing parts 112,121,130, and 131. In the housing part 130 a pressure generator connection 101 is provided which can be connected with a pressure medium source. A channel 102 branches off from the pressure generator connection 101 as does a bore 103, which bore 103 leads through the housing parts 112 and 121 to the bore section 124 provided in the housing part 131.

The channel 102 is followed by a valve device consisting of the valve seat 104 and of the valve closure member 106 designed as a ball. When closed, the valve device separates the channel 102 from the chamber 111 wherein 2 second valve device is provided which is composed of a valve closure member 113 likewise designed as a ball and of the appertaining valve seat 114. The two valve closure members 113 and 106 are supported in a guide sleeve 109 and acted upon in the closing direction by means of a common spring 107 likewise provided in the guide sleeve 109. The guide sleeve 109 has a C-profilelike cross-section, i.e., it is provided with an axially extending slot 108.

A connection bore 110 branches radially off from the cylindrical chamber 111 and is connectible with a brake, for instance, with the afore-described clutch type disc brake. Separated by means of the valve device 113,114, the chamber 111 is axially followed by a further chamber 116 having a cylindrical shape. On its front side facing the valve seat 114, the chamber 116 is confined by the smaller front face 117 of a differential piston 125.

With its piston portion 119 having a smaller crosssection than the second piston portion 122 the differential piston 125 is sealed and axially displaceably supported in the bore belonging to the chamber 116, while its piston portion 122 of larger cross-section is completely accommodated in the bore 120 where it is sealed and guided in an axially displaceable manner. In the front face of the bore 120 pointing towards the chamber 116 a bore 118 is provided which has communication with the atmosphere. The pressurisation surface 123 of the piston portion 122 communicates with the pressure generator connection 101 via the bore section 124 and the bore 103.

Axially passed through the chamber 116 and provided between the front face 117 and the valve closure member 113 is a tappet 115 which is guided within the valve seat 114 in an axially displaceable manner and which is provided with grooves on its surface area, these grooves extending axially and being distributed over the circumference.

In the unpressurised condition the clearance valve is in the position illustratred in Figure 3.

With the clearance valve being pressurised via the pressure generator connection 101 , pressure is active in the channel 102 as well as in the bore section 124. Due to the surface ratio at the differential piston 125, the latter moves in the direction of the valve seat 114 and thus, via the tappet 115, opens the valve closure member 113 against the force of the spring 107. In doing so, the volume displaced out of the chamber 116 is urged into the chamber 111 or rather into the connection bore 110 and thus into the brake. The volume of chamber 116 of this example is so dimensioned as to equal the sum of all volumes received by the brake's actuating pistons to be actuated and resulting from the product of clearance multiplied by the corresponding actuating piston diameters. Further, all elasticities occurring in the brake are included in the calculation.

As long as the brake pads of the brake are free from wear the passage 105 of the valve seat 104 remains closed. After the termination of the brake application the brake being ventilated again by the resetting device, the pressure medium volume is thus displaced back into the chamber 116 via the brake lines and the chamber 111.

If in the course of time, wear makes itself evident at the brake pads or the brake discs, in the case of a brake application - with the pressure in the pressure generator connection 101 further increasing - further required pressure medium can flow via the valve device 106, 104 after the differential piston 125 has displaced the entire volume from chamber 116 into the brake line or rather the actuating pistons. Upon a subsequent pressure decrease in the pressure generator connection 101, the valve device immediately closes again and the actuating pistons can return into their initial positions during the resetting action as predetermined by the volume in chamber 116. Thereby, automatically, further amounts of pressure medium are always supplied into the hydraulic circuit between brake and connection bore 110 as is required for maintaining a permanently constant clearance. Thus an active clearance as well as an automatic adjustment of the same in the brake, is ensured whereby a constant responding behaviour is guaranteed.

Figure 4 shows another embodiment of the clearance valve especially suited for brakes where smaller volumes have to de displaced. As compared with the embodiment of Figure 3, essentially, the difference consists in that the differential piston 125, the tappet 115, and the valve device 113, 114 are not provided and are replaced by a self-resilient diaphragm 160 instead. In the case of those parts corresponding to each other, the same reference numerals as in Figure 3 are used in the following.

In Figure 4, the position of the clearance valve is shown in the unpressurised condition. Upon a pressurisation via the pressure generator connection 101, the valve device 104, 106 at first remains closed while the pressure active in the bore section 124 displaces the diaphragm 160 towards the surface 161, thus reducing the chamber 116 in size. The volume displaced out of chamber 116 is displaced towards the connection bore 110, thus pressurising the actuating pistons of the brake. The diaphragm 160 is fastened in a sealed manner in the housing by means of corresponding devices 162.

Corresponding in terms of operation to the valve described in Figure 3, via the valve device 104,106, here it is also possible to supply the volume additionally required in case of pad wear, after the diaphragm 160 has abutted against the surface 161. Upon a subsequent pressure decrease in the pressure generator connection 101 the valve device 104, 106 immediately closes again and volume can flow back into the clearance valve only to the extent of the capacity of the chamber 116.

Claims (12)

1. A clutch type disc brake of the kind having a housing, at least two axially displaceable brake discs arranged in the housing, at least four friction rings out of which in each case two are arranged on both sides of one brake disc, and an actuating device having at least two actuating cylinders with actuating pistons arranged therein, which actuating device in each case is arranged between two friction rings, characterised in that the actuating cylinders (6) are at least partially arranged in two central pieces (1,2) of the housing, these central pieces (1,2) of the housing forming a hollow space (5) provided with a coolant inlet and with a coolant outlet (a,b).

2. A clutch type disc brake as claimed in claim 1, characterised in that at least two pad resetting devices (24,25) are arranged in the area between two friction rings.

g, A clutch type disc brake as claimed in either of the preceding claims, characterised in that there are provided outside cooling plates (16) with coolant connections (20).

4. A clutch type disc brake as claimed in any one of the preceding claims, characterised in that a number of actuating cylinders (6) are connected by linking bridges (10) which are provided in the hollow space (5) and the two flange surfaces (G,H) of which in each case are not lying parallel to each other.

5. A clearance valve for a clutch type disc brake as claimed in any one of the preceding claims, comprising a housing, a pressure generator connection, a pressure consumer connection, and a valve device provided between the pressure generator connection and the pressure consumer connection, characterised in that a connection (110) connectible with at least one pressure consumer communicates with the pressure generator indirectly, on the one hand, via a movable wall such as a piston (125) or a diaphragm (160) and, on the other hand, directly with the pressure generator connection (101) via a prestressed seat valve (104,106).

6. A clearance valve as claimed in claim 5, characterised in that the volume displaceable by the movable wall equals the volume which has to be carried off out of the pressure consumer for ventilating the brake.

7. A clearance valve as claimed in claim 5 or 6, characterised in that a further seat valve (113,114) is provided which is actuatable by the movable wall.

8. A clearance valve as claimed in claim 7, characterised in that the two seat valves (104,106 and 113,114) are prestressed by a common spring (107).

9. A clearance valve as claimed in any one of claims 5 to 8, characterised in that the piston serving as a movable wall is a differential piston (125) whose larger pressurisation surface (123) is pressurisable by the pressure of the pressure generator.

10. A clearance valve as claimed in any one of claims 5 to 8, characterised in that the clearance valve is used in combination with a pad resetting device (24,25) of a brake, in particular of a clutch type disc brake as claimed in claim 2.

11. A clutch type disc brake substantially as described with reference to the accompanying drawings.

12. A clearance valve for a clutch type disc brake substantially as described with reference to the accompanying drawings.